Here on LA Times, I read an article about how amazon.com prices "mysteriously" increase when you put them in your shopping cart and check them out later in a day or two. 

Here is an excerpt from the article about how things actually would look stupid in a real life situation:

Imagine this: You go to a bookstore, browse, choose a couple of volumes. But you don't want to carry the books around. So you ask the clerk to hold the tomes until Saturday, when you'll come back to buy them.

When you return, the bookseller hands you the items but advises you that he's raised the prices. "I knew you were hot to buy them," the clerk says, "so I figured I could make a few extra bucks."

This is what happened to me when I tried the same thing:

Important Messages

Please note that the price of Leo Africanus has increased from $11.53 to $12.03 since you placed it in your Shopping Cart. Items in your cart will always reflect the most recent price displayed on their product detail pages.

Please note that the price of BMW 3 Series (E36) Service Manual: 1992-1998 (BMW) has increased from $50.37 to $52.77 since you placed it in your Shopping Cart. Items in your cart will always reflect the most recent price displayed on their product detail pages.